No need to worry. I work on a Mac and my wife on a PC and we share documents every day without problems.

Davids question looks like the best fit for me. But additional: Do you have facing pages? Does this happen with an even and/or odd number of pages?

But then he has no text flow from line to line, if that is what he wanted. I could only think of a workaround with rectangles and text wrap, but that would be very much work and not very flexible.

Selecting items on different spreads can be very dangerous, because you could delete something that is selected and you don’t see it because it’s on another page. So I don’t know if I would like this function. For moving pictures around I could use split windows.

For the text there is the conditional text feature (https://indesignsecrets.com/finally-conditional-text.php)

If you lock the elements (or the whole layer), you can change the content but not the position of the frames, if this is what you want to do.

Adobe says:

Scaling vs. resizing objects

Resizing and scaling are different actions in InDesign. Resizing is simply changing the Width and Height values of an object. Scaling involves using a percentage value related to the original scale (100%) of the frame.

The difference between resizing and scaling isn’t always apparent. A good way to see the difference is to resize and scale a text frame that has a stroke applied to it. When you double the size of the text frame, the text size and stroke weight remain the same. When you double the scale of the text frame, the text size and stroke weight also double.

(https://helpx.adobe.com/indesign/using/transforming-objects.html)